Vascular smooth muscle cell (VSMC) migration from media to intima and their proliferation in intima are important factors in the pathogenesis of atherosclerosis and restenosis following angioplasty. Nuclear factor of activated T cells (NFATs) are a group of transcription factors that belong Rel family. Initial studies from other laboratories have indicated that these transcription factors play an important role in cardiac development and hypertrophy. Work from our laboratory showed for the first time that NFATs play a critical role in mediating VSMC migration and proliferation in response to receptor tyrosine kinase (RTK) and G protein-coupled receptor (GPCR) agonists. In addition, we showed that blockade of calcineurin-NFAT activation signaling substantially inhibits balloon injury-induced neointima formation in a rat carotid artery. In the current grant proposal we seek to study the molecular mechanisms by which these transcription factors mediate VSMC proliferation induced by both RTK and GPCR agonists. Furthermore, we also want to identify the specific member of the NFAT family of transcription factors that mediates RTK and GPCR agonist-induced VSMC proliferation and balloon injury-induced neointima formation. In order to achieve these goals we will address the following three specific aims: 1. NFATs mediate both RTK and GPCR agonist-induced cyclin A expression and, thereby, modulate the activity of cyclin-dependent kinases 2/1 (CDK2/1) leading to S phase progression and proliferation of VSMC. 2. To identify the NFAT regulatory motifs in the promoter region of cyclin A that mediate its expression by both RTK and GPCR agonists in VSMC. 3. To identify the specific member of the NFAT family of transcription factors involved in injury-induced cyclin A expression and neointima formation in rat and mouse carotid arteries. The results of these three specific aims will provide novel information in regard to identification of specific member(s) of the NFAT family of transcription factors and its target gene(s) in mediating VSMC proliferation induced by both RTK and GPCR agonists in vitro and injury in vivo. Such knowledge will be useful in the development of potential therapeutics targeting inflammatory vascular diseases such as atherosclerosis and restenosis.